1. Field of the Invention
The present invention is broadly concerned with finely divided (preferably nanoscale) composite materials which have significant utility in the destruction of chlorocarbons, fluorocarbons and other toxic or undesirable fluids. More particularly, the invention pertains to composite materials including first metal oxide particles, preferably MgO, at least partially coated with an extremely thin layer of a different second metal oxide such as a transition metal oxide, e.g., Fe.sub.2 O.sub.3. Composites in accordance with the invention have greatly enhanced abilities to destructively adsorb undesirable fluids such as gases or liquids.
2. Description of the Prior Art
The increasing amounts of chlorocarbons and chlorofluorocarbons in the environment has given rise to the need to find easy and effective ways to destroy these gases without producing toxic byproducts. The most widespread groups of chlorinated compounds are the polychlorinated biphenyls (PCBs) which have extremely high thermal stabilities and are used as lubricants, heat transfer fluids, plasticizers, and transformer fluids; and cleaning solvents such as CCl.sub.4, CHCl.sub.3, and C.sub.2 Cl.sub.4. Additionally, large stores of obsolete or overaged pesticides, herbicides, mixed wastes and nerve gases exist around the world, and the safe and effective destruction of these materials is of increasing concern.
These considerations have prompted a number of investigations to determine the most feasible way of handling and destroying various undesirable substances. Some of these destructive techniques involve incineration or catalytic oxidation. Another approach depends on surface active reagents that strip heteroatoms from the toxic gases and allow only the release of non-toxic hydrocarbons or carbon oxides. For example, the destructive adsorption of organophosphorus compounds on MgO causes the phosphorus atoms to be immobilized as a strongly bound residue, with the only volatile organic products being CH.sub.3 OH and HCOOH. This same chemistry has been applied to the destruction of chlorocarbons using reactants such as MgO or CaO.
While destructive adsorption techniques appear promising and have favorable thermodynamics, the cost thereof has been considerable, owing principally to the fact that, to be effective, the adsorptive reagents must be very finely divided for maximum surface area. Moreover, these reactions are non-catalytic and depend entirely upon molecular reactions at the surface of the reagents.
This is accordingly a real and unsatisfied need in the art for improved destructive adsorption reagents which have enhanced destructive efficiencies.